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This week's Spotlight on Research is with Dr John Regan Marie Skłodowska-Curie Research Fellow and DCU School of Mathematical Sciences

You research how really, really big black holes formed in the early Universe. How big are these black holes?

“The main way we classify black holes is by their mass, and the ones I look at are supermassive, which means their mass is hundreds of thousands or even millions of times the mass of our Sun.”

What is the particular puzzle that interests you about these supermassive black holes?

"One of the interesting things we see when we look back 13 billion years ago at the early stages of the Universe, when the Universe was very young, is that supermassive black holes formed then.But this is puzzling.”

Why?

“One of the main theories about how black holes form is that a star collapses in on itself and then gravity takes over, and the black hole ‘eats’ other objects and that is how it grows over time. But in the early Universe we would not expect normal run-of-the-mill stars to be that massive, so it is not clear how some of the black holes that we can see formed back then got so big so quickly.”

You have a solution though…

“Yes, we have built and run mathematical simulations based on the observations of the early Universe, and we have just published a paper in Nature Astronomy this week that we think could explain one way in which these supermassive black holes formed.”

Go on…

“Our proposition is that if two galaxies are next to each other in this early Universe, one may start irradiating the other, bombarding it with radiation. This could disrupt the normal formation of stars in that ‘zapped’ galaxy, so that it can’t form stars. But the galaxy keeps growing and eventually you have this huge pile of mass and gravity takes over, forming a massive black hole.”

So the irradiated galaxy collapses in on itself?

“Pretty much. It would explain how a black hole could get supermassive so quickly in that early Universe environment.”

How did you become interested in the early Universe?

“I think I was born interested in space. And for a long time I have been fascinated particularly by the theory of how objects in space form. Studying the early Universe is a relatively ‘clean’ time to look at the theory of how objects like black holes form, because there were fewer chemical elements there at that time.”

What do you like about being an astrophysicist in Ireland?

“I think in Ireland we are building up a group of researchers who are doing interesting and related things in astrophysics, and we get together and talk about them. I think some really nice research has been growing here.”